Railway switch and signal control and interlocking apparatus



B. A. MCCANN Filed Oct. 7, 1944 RAILWAY SWITCH AND SIGNAL CONTROL AND INTERLOCKING APPARATUS my MWMN INVENTOR v fianald A. lf Calzzz.

H15 ATTORNEY K UHIL NM %N MSEHT Aug. 5, 1947.

. NM RS N Patented Aug. 5, 1947 RAILWAY SWITCH AND SIGNAL CONTROL AND INTERLOCKIN G APPARATUS Ronald A. McCann, Swissvale, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa, a corporation of Pennsylvania Application October 7, 1944, Serial No. 557,625

15 Claims.

My invention relates to railway traffic controlling apparatus, and more particularly to a system of relays for electrically interlocking track switches and signals, suitable for use on railways employing automatic train stops where the control limits for the signals overlap to permit them to be more closely spaced and to provide adequate stopping distances for high speed trains operating on a short headway.

In systems of this character the control limits for the signals which govern trains approaching aninterlocking plant extend into or through the plant and consequently include sections containing track switches which may properly be operated after the approach signals have been cleared, providedthe home signals are at stop. Since the control circuit for the approach signal conforms to the route set up through the plant, the control of the. signal will-be transferred from one route circuit to another when the switches are operated.

One object of my invention is to prevent an approach signal which has been cleared from being put tostop-as the result of the operation of a track switch in the route governed by the signal. This is accomplished by extending the locking limits for the switches, when the approach signal is cleared, to correspond with the control limit for-the signal, the extended locking permitting the switches to be operated only if the condition'of the route which would be established by their operation is such as to maintain the approach signal at clear.

A feature of my invention is the provision of time-controlled means for rendering the extended locking ineffective if thespeed of the approaching train is relatively slow, the control limits for the approach signal being correspondingly shortened to permit it to clear even though the extended locking section is occupied.

Another object of my invention is the provision of means for automatically operating a trailing switch located in a route governed by an ap proach signal, either in response to the operation ofthe controlmeans for clearing the signal or in respon e to the operation of the control means for a facing switch, whereby the track switches are operated in a predetermined order and the approach signal is maintained at clear during the transferof its control from one route circuit, to another.

I shall describe one form of apparatus embodymg my invention, and shall then point out the novel features thereof in claims.

In theaccompanying drawing, the diagram at the top shows a track layout comprising an interlocking plant including the home signals 2, i, 6, 8 and 12 for governing trafiic movements over the crossover switches Al and Bi and a single switch 3, with two approach signals to and it for governing the movement of traffic approaching the plant from the right. To simplify the drawing I have shown in detail only the circuits required to illustrate my invention as applied to one of the approach signals, namely to signal Ill, the circuits as shown including the control circuits for this signal and the switch control and locking circuits associated therewith.

The tracks which extend through the layout for simplicity are each represented by a single line in the track plan. It is to be understood that the tracks are divided into track sections by insulated joints 1 in the usual manner. The track sections are provided with track circuits, identified by the reference character '1 with distinguishing numerical prefixes, each such circuit having a source of current B at one end and a track relay R, at the other end, identified by the same number. interlocking limits provide detector locking sections for the track switches, as for example, sections IT and AIT for the crossover switches Al and BI, and section 3T for switch 3. Sections ST and GT are extended locking sections for the switches and are included in the control limits for signal It, along with the detector sections and section IOT, while section AIUT is an approach section for indicating when a train is approaching signal 10.

The interlocking plant may be controlled in any suitable manner, as for example, by manually operable switch and signal levers, or by a system of route control, such as that illustrated in Letters Patent of the United States No. 2,301,- 297, granted November 10, 1942, to Lloyd V. Lewis,

for Railway traffic controlling apparatus, and in my prior application for Letters Patent of the United States, Serial No. 539,234, filed June 8,

1944, for Interlocking control apparatus, now

Patent No. 2,387,853,.issued October 30, 1945,-

wherein circuits for the route control of a layout corresponding to that of signals 2, l, 6 and 8 and the crossover AlBl are shown.

A shown herein, each switch is operated by a power switch machine AIM, BlM or 3M, controlled by a polarized switch control relay [W or 3W. Each switch controls a polarized switch indication relay IP or 3P which is energized in the normal or reverse direction only when the switch is mechanically locked by its switch ma- The track sections within thechine in the corresponding normal or reverse position. Each switch control relay W and the associated switch indication relay P in corresponding normal or reverse positions jointly control a normal correspondence relay INC or 3NC and a reverse correspondence relay IE or 3R0, as shown.

The switch control relays IW and 3W are governed by circuits similar to those of my prior application for Letters Patent of the United States No. 539,234, each such relay being operable to normal or reverse when the switch locking relay ILS or 3L5 is energized to correspond with the position of a manually controllable polar stick control relay IV? or 3VP controlled by an individual switch lever IV or BV.

The relays VP are operable to normal or reverse when the associated locking relay LS is energized by operating the corresponding lever V manually to the left or right from its inactive center position, whereupon the associated relay W is operated to a corresponding position, provided a circuit therefor is available. In its center position the lever contact is included in a pick-up circuit for the associated switch locking relay LS to provide non-storage switch control, whereby the lever is efiective to control the switch only if it is operated at a time when the switch is free to respond as manifested by the energization of the switch locking relay.

The relays VP and W may also be operated by connecting terminal In or IT, and terminal 3n or 31', to terminal C by the operation of other means, not shown, such as a system of route selecting relays controlled by manually operable route buttons as illustrated in my prior application.

The locking circuits by which the relays LS are energized to permit operations of the relays VP and W are closed only when trafilc conditions are such as to permit the track switches to be operated, over contacts of the track relays R and of approach locking stick relays AS controlled by the signals. The circuits for relay ILS are divided into two portions as required in connection with the route storage feature of my prior application, one of which portions includes the positive locking, that is, the detector and approach locking associated with the home signals, and controls a locking relay I LR, while the second portion is controlled by relay ILR and includes the conditional or extended locking associated with the approach signal Ill.

The signals may be of the color light or searchlight type, and as shown herein each has a control relay or mechanism such as the relay 6H or IllI-I which is energized to clear the corresponding signal 6 or ID and to release the corresponding approach locking relay GAS or IIlAS to lock the switches in the route governed thereby. A time element relay GTE or IGTE provides the usual time locking protection when a signal is put manually to stop in front of an approaching train.

Since the route governed by the approach signal I0 is the same as that for signal 6, it is unnecessary to designate the route desired in order to clear signal IG, and the latter is shown as controlled by a stick relay HIPS, similar to the entrance stick relays of the route system of Patent No. 2,301,297. Relay IBPS is picked up by pressing a signal button IEIPB and is released by the track relay IOR when a train passes signal ID at clear. Relay IDPS is controlled also by relays 3LS, 3NC and IRC so that it is p eve t d from responding unless a route governed by signal I0 is available.

It is to be understood that an automatic train stop device 5 is provided at each signal location, as shown adjacent signal G, by which the train brakes are applied in case a train overruns a stop signal; A train passing signal It) at clear and overrunning signal 6 at stop will thus incur an automatic brake application by which it will be brought to stop within the control limits of si nal ID, that is to say, in section GT or 8T, if the train speed is high.

If the speed of the train is relatively slow, a shorter stopping distance suffices, and to take advantage of this fact a time element AIG'I'E is provided by which the time required for an approaching train to pass through section AIOT is measured. When the train is moving slowly, relay AIIJ'I'E completes its operation before the train passes signal ID, and shortens the control limits for the signal and also renders the extended locking inefiective. When relay AIOTE is fully energized, the control limits for signal I0 extend only to the opposing signal 2 or 4.

When the apparatus is in its normal condition, as shown, the approach locking relay GAS is held energized over a stick circuit which extends from the supply terminal B of a suitable local source of current at back contact I5 of the signal control relay GH, over the front contact IG and winding of relay GAS to the common return terminal C of the same source. Although the circuits for relay 5H are not shown, it will be understood that'thcy are of the same type as the circuit for relay NIH and that relay GH may be energized by manual control to clear signal 6 for ran-approaching train, whereupon relay GAS releases, and that relay 6H is released by the track relay AIR when the train passes the signal, whereupon relay GAS is reenergized over back contact I I of relay AIR. Relay GH may also be released .by the operator to put signal 6 manually to stop, in which case relay GAS picks up over contacts I8 and I9 of relays I GR and AIOR, providing the approach zone comprising sections IOT and AIUT is unoccupied. Otherwise the time element relay GTE- becomes energized over back contact I6 of relay GAS and completes a circuit for relay GAS after a suitable time interval to provide the usual time locking. It

is to be understood that the circuits for the otherapproach locking relays associated with home signals such as the relays ZAS, 4A8, GAS and IZAS are similarly controlled by the approach track relays of sections in the rear and by the detector track relays of the sections in front of the correponding signals. The locking conditions for the approach signal ID are th same as for signal 6 and consequently relay IDAS is controlled by the same track relays as relay GAS, as shown, and it will also be understood that relay I IAS is controlled lik relay IZAS,

The switch locking relay ILR as shown is normally energized over a circuit extending to terminal B at front contact I I of relay ZAS and including front contacts of the approach locking relays 4A8, GAS and GAS and of the track relays IR, AIR and 3R. A front contact I3 of relay 3R0 bridges the contacts of relays IAS and GR in the circuit when route 2-I2 is set up, to permit the crossover to be reversed to set up the parallel route 64. Relay ILS is normally energized over a circuit extending from terminal B at contact 20 of relay ILR over contact 2| of relay I OAS through relay ILS to terminal C over th center contact 22 or lever IV or its own front contact 23.

Relay 3LS is normally energized over a circuit extending from terminal B at front contact 24 of relay ZAS and includin front contacts of the approach locking relays GAS, IOAS, I2AS and MAS and of the track relays A IR and 3R. A front contact 25 of relay IRC bridges the contacts of relays GAS, I OAS and AIR in this circuit When route 6-4 is set up, to permit switch 3 to be reversed to set up a parallel route.

The switch control relays IW and 3W are arranged to be energized over front contacts of relays ILS and 3LS, respectively, in a direction corresponding to that of relay IVP or 3VP by connecting their circuits to terminal C of the local source of current over a branch of the circuit for relay IVP or 3VP, and when relay ILS or 3LS releases, relay IW or 3W is held energized over its own polar contacts and corresponding contacts of the associated indication relay IP or 3P, releasing when the locking relays become reenergized. Relays IW and 3W thus are normally deenergized with their. polar contacts in their last operated position, this being assumed to be the normal position as shown.

The switch indication relays IP and 3P are normally energized, and as shown their polar contacts are in the left-hand or normal position so that the normal correspondence relay INC is energized over the circuit from terminal B over contacts 26 and 21 of relay IP through relay INC to terminal C at the normal contact 28 of relay IW, and relay 3NC is similarly energized by relays 3P and 3W.

Havin thus described the various elements of the system of my invention, I shall now describe its operation under difierent assumed conditions.

I shall first assume that the apparatus is i the condition shown in the drawings and that the operator, desiring to clear the approach signal It in order to advance an approaching train to signal 6, presses the push button IDPB completing a circuit from terminal B at contact 29 of relay 3L8 or contact 30 of relay 3N0 over contact 3| of relay I OR and contact 32 of button I OPB through relay IOPS to terminal C. Relay IBPS picks up, completing a stick circuit including the normally closed pull contact 33 of button IIlPB, and connecting terminal B at contact 34 to the circuit for relay IBH, which circuit is completed over contact 35 of relay INC and contacts 36 to 43 of relays 6R, 3NC, 3R, AIR and I BR through relay lIlI-I to terminal C.

Relay IIlH picks up, closing contact 4| to clear signal I I], and opening its back contact 42 releases relay IDAS, which by opening its contact 43 releases relay 3L8, thereby opening the control circuits for relays 3V? and 3W to lock switch 3 normal. Relay IIlAS also opens its contact 2| in the circuit for relay ILS, but this contact is now bridged by the normal contact 41 of relay IP and the front contact 48 of the track relay 8R so that relay ILS remains energized unless signal 6 is cleared to release relays GAS and ILR.

If now an approaching train enters section AIOT, the time element relay AI OTE is energized over contacts 44 and 45 of the track relays AIUR and I OR, and is thereby set into operation to close its front contacts after a measured time interval. If the train speed is so high that the train enters section IIIT to cause relay IOR to release and open its front contact 45 before contact 46 of relay AIOTE closes, relay AIIlTE returns to its normal released position without closing its front contacts.

I shall now assume that the operator holds signal 6 at stop, desiring to advance another train approaching signal I4 to section 6T ahead of the train approaching signal I0. Since the route for the other train conflicts with the one controlling signal II), it can be set up with signal [0 at clear only after the crossover AI-BI has been reversed to provide an alternative route to maintain signal III at clear. If the train governed by signal I0 happens to overrun signal 6 at stop, the distance originally provided for stopping it by the operation of the automatic train stop 5 includes sections AIT, 3T and GT. With signal 6 at stop, and the approaching train in section AIUT or IIJT, relay IUAS remains released and switch 3 is locked normal as long as the crossover switches are normal, due to the fact that contacts 43 and 25, which are in multiple in the circuit for relay 3LS, are both open. Relay ILS is however now energized over contact 20 of relay ILR, the normal contact 41 of relay IP and contact 48 of the track relay 8R so that the crossover switches AIBI are free to be operated to reverse to close contact 25 of relay IRC and thereby energize relay .3LS to unlock switch 3, provided sections AIT, IT and ST of the alternative route are unoccupied to maintain adequate stopping distance measured from signal 6. If the speed of the train approaching signal Ill is slow, relay AIOTE completes its operation and closes its contact 46 before the train enters section IDT, thereby establishing a stick circuit over back contact 45 of relay IUR so that relay AIBTE is held energized until the train vacates section IIlT. In this case contact 48 of the track relay 8R in the circuit for relay ILS is bridged by contact 49 of relay AIllTE, so that relay'ILS becomes energized and the crossover is free to be operated to reverse provided only sections AIT and IT of the alternative route are unoccupied.

In preparation for setting up route I22, therefore, the operator moves lever IV to its right-hand position to complete a circuit from terminal B at contact 50 of relay ILS through the lower winding of relay IVP to terminal C at the right-hand contact 22 of lever IV, operating relay IVP to reverse and thereby closing a circuit from terminal B at contact 54 of relay IVP through relay IW over contacts 52 and 5I of relay ILS and contact 53 of relay IVP to terminal C at contact 22 of lever IV. Relay IW by closing its neutral contact 55 and reverse polar contact 56 energizes the switch machine AIM and BIM to operate the crossover switches to reverse, whereupon relay IP becomes energized in the reverse direction, releasing relay INC and energizing relay IRC to close contact 25, thereby energizing relay 3L8 to permit switch 3 to be reversed.

Considering now the circuit for relay I OH, it will be seen that after contact 35 of relay INC opens, the circuit is maintained closed during the operation of the crossover switches over contact 51 of relay IR, and contact 58 of relay 8R or contact 59 of relay AIOTE, and thence as already traced over contacts 36 to 40. Whenthe crossover switches become locked reverse with relay IRC energized, contacts 36, 31 and 38 in the circuit for relay IflH are bridged by contact 60 of relay IRC, and contacts 29 and 30 in the circuit for relay [OPS by contact 6I of relay IRC.

It will be seen that in addition to the two branches of the circuit for relay IIIH by which signal II] is cleared when switches AI-BI are normal or reverse, in accordance with the route established thereby, the circuit has a third branch 7 established while the switches are inv transit, provided both routes are available. It follows that as soon as the crossover is indicated reverse, switch 3 may be operated to reverse and signals l2 and 14 may be cleared, signal l remaining at clear.

When the crossover is reversed, the circuit for relay ILS is shifted by the reversal of contact 41 of relay IP to include contacts 6| to 64 in place of contact 48 so that as long as relay IOAS is released, relay lLS releases when signal I'2 or M is cleared and remains released to positively lock the crossover reversed until section 3T of the route governed by these signals is vacated and their approach locking relays are reenergized. The crossover is then conditionally locked reverse, its locking depending upon the condition of section GT and upon the speed of a train approaching signal Hi. It is to be noted, however, that in order to maintain a route circuit for relay lliI-I, switch 3 must be in its normal position when the crossover is operated from reverse to normal.

I shall now assume that the train in the route governed by signal I2 has vacated section 3T and that the operator desires to set up the route 8-4 for a train on the lower track, signal Ill remaining at clear, with signal 6 at stop, as in the preceding example. As soon as relay ILS is energized over contact 63 of relay 3R and contact 64 of relay ER or contact 65 of relay AIUTE, relay IVP may be restored to normal by connecting terminal C to wire In to energize its upper winding, either by placing lever IV in its left-hand position or by the operation of the route relays of my prior application as required to set up the route 84. Relay lW does not respond to the operation of relay IVP to normal but remains deenergized with its polar contacts reversed, because its circuit is open at contacts 66 and 61 of relays lllAS and 3N0, indicatin that signal ID has been cleared and that route 62 is unavailable because switch 3 stands reversed.

Relay 3L8 is now energized over contact 25 of relay IRC, and the closing of the normal contact 69 of relay IVP completes circuits extending to terminal C at contact 68 of relay HIPS to succes sively operate relays 3VP" and 3W to normal, causing switch 3 to assume its normal position, thereby releasing relay 3R0 and energizing relay 3N0. The closing of contact 31 of relay 3NC completes the branch of the circuit for relay llJI-I which includes contact 38 of relay 3R, contact 36 of relay ER or contact ill of relay AIBTE, and contacts 51 and 58 of relays IR and BB. Relay ILS is held energized over the branch of its circuit including contacts 6| to 63, contact 64 or 65, and contact 48 or 49. The closing of contact 61 of relay 3N0 energizes relay IW in the normal direction over the normal contacts 53 and 54 of relay IVP so that the crossover switches Al-Bl are operated to normal. Relay lRC releases, but relay IOPS is held energized over contact 30 of relay 3NC. Relay 3LS releases to lock switch 3 normal, due to the opening of contact 25 of relay IRC. Relay lP assumes its normal position so that its contact 41 bridges contacts 6l--64, etc. in the circuit for relay ILS and relay INC becomes energized, its contact 35 bridging contacts 51-59 in the circuit for relay IUH, so that signal H] is maintained at clear. If signal 8 is now cleared, the crossover is positively locked normal by the release of relays BAS and ILR, and after these relays become re-energized, is conditionally locked normal depending upon the condition of section 8T and upon the speed of a train approaching signal ID as indicated by the position of contacts 48 and 49, in the circuit for relay lLS.

I shall next assume that the switch 3 stands reversed for the movement of a train over the route l2-2 governed by signal l2, but that the crossover stands normal with signals 6 and ID at stop. In this case signal l0 cannot be cleared because the circuit for relay MP8 is open as long as relays 3LS and SNC remain deenergized, and in the circuit for relay IilI-I contacts 31 and 60 of relays 3NC and IRC are both open. As soon as the train vacates section 3T, relay 3LS becomes reenergized to prepared a circuit at its contact 29 for relay IGPS. If button IOPB is now pressed, relay H1 PS becomes energized, closing its contact 68 tooperate relays 3VP and 3W to normal, thereby operating switch 3 automatically to normal and energizing relay 3N0, whereupon relay IIJH becomes energized to clear signal In, provided the route governed thereby is unoccupied.

It will be seen therefore that the manipulation of the system is facilitated by the fact that it is unnecessary for the operator to set up a route through the plant in order to clear an approach signal such as signal Hi, this signal governing trafiic movements over whatever route may be indicated by the positions of the facing switches, such as switch Al, since the operation of its control button IOPB results in the automatic operation of the trailing switches, such as switch 3, to the positions required for such route. Furthermore, the switches are operated in a predetermined order so that when the route governed by the approach signal is changed by the operation of a facing switch, the trailing switches such as switch 3 are found in the proper positions to maintain a circuit for the approach signal.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein Within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. Railway trafiic controlling apparatus comprising a detector section of railway track including a track switch, a home signal for governing trafilc movements into said section in a direction facing the switch, two extended locking sections beyond the switch, one in the route over the switch in its normal position and the other in the route over the switch in its reverse position, an approach signal governing trafiic approaching the home signal, a control circuit corresponding to the route established by the track switch and adapted to be manually closed to clear the approach signal only when the detector section and the extended locking section in the route established by the switch are both unoccupied, a switch locking relay which when deenergized prevents the operation of the switch, an energizing circuit for the switch locking relay controlled by contacts which when closed indicate that the detector section is unoccupied and that the home signal is at stop, and means governed by the control circuit for the approach signal for controlling the circuit for said switch locking relay to insert therein contacts selected by the track switch which indicate the condition of that one of said extended locking sections which is not included in the route established by the switch,

9 said means being rendered effective upon the closing of the control circuit for the approach signal when the extended locking section in the established route becomes unoccupied, to open the circuit for the switch locking relay unless the other extended locking section is also unoccupied.

2. Railway trafiic controlling apparatus comprising a detector section of railway track including a track switch, a home signal for governing traiiic movements into said section in a direction facing the switch, two extended'locking sections beyond the switch, one in the route over the switch in its normal position and the other in the route over the switch in its reverse position, an approach signal governing traffic approaching the home signal, control circuits selected by the track switch and closed to clear the approach signal only when the detector section and the extended locking section in the route established by the switch are both unoccupied, a switch locking relay which when deenergized prevents the operation of the switch, an energizing circuit for the switch locking relay controlled by contacts which when closed indicate that the detector section is unoccupied and that the home signal is at stop and also by a contact which when closed indicates that the approach signal is at stop, and means for maintaining the circuit for said locking relay closed even though said approach signal has been cleared provided both said extended locking sections are unoccupied.

3. Railway traffic controlling apparatus comprising a detector section of railway track including a track switch, a home signal for governing traffic movements into said section in a direction facing the switch, two extended locking sections beyond the switch, one in the route over the switch in its normal position and the other in the route over the switch in its reverse position, an approach signal governing trafiic approaching the home signal, control circuits selected by the track switch and closed to clear the approach signal only when the detector section and the extended. locking section in the route established by the switch are both unoccupied, a first and a second switch locking relay, an energizing circuit for the first locking relay controlled by contacts which' when closed indicate that the detector section is unoccupied and that the home signal is at stop, an energizing circuit for the second locking relay including a front contact of the first locln'ng relay and a contact closed by the approach signal in its stop position bridged by a contact closed when the approach signal is cleared for a movement over either route provided the extended locking section in the other route is unoccupied, and means for preventing the operation of the switch unless said second locking relay is energized.

4. In combination with a detector section of railway track including a track switch, a home signal for governing trafiic movements in the facing direction over the routes established by the operation of the track switch to normal and reverse, extended locking sections beyond the switch in said routes, an approach signal for governing traflic approaching the home signal, a con- I trol circuit for clearing the approach signal closed when the detector section and the extended locking section beyond in the established. route are both unoccupied, a switch locking relay, means controlled by the home signal for controlling said locking relay to prevent an operation of the switch unless the home signal is in its stop position and the detector section is unoccupied, and

means controlled by the approach signal for controlling said locking relay to prevent an operation of the switch to establish a difierent route after the approach signal has been cleared unless the extended locking section in said different route is unoccupied.

' 5. In combination with a detector section of railway track including a track switch, a home signal for governing traffic movements in the facing direction over the routes established by the operation of said track switch to normal and reverse, an automatic train stop adjacent the home signal forapplying the brakes of a train on passing said signal at stop, an approach signal governing trafilc approaching the home signal, a control circuit for clearing the approach signal closed only when the established route is unoccupied for a given distance within which a high speed train may be stopped if its brakes are applied by said train stop, a switch locking relay, means controlled by the home signal for controlling said locking relay to prevent the operation of the switch unless the home signal is in its stop position and the detector section is unoccupied, and means controlled by the approach signal for controlling said locking relay to prevent an operation of the switch to establish a diiierent route after the approach signal has been cleared unless such route is unoccupied for said given distance.

6. In combination with a detector section of railway track including a track switch, a home signal for governing trafiic movements in the facing direction over the routes established by the operation of the track switch to normal and reverse, extended locking sections beyond the switch in said routes, an approach section having an approach signal at its exit end for governing traffic approaching the home signal, a timing relay, means for energizing said timing relay only when a train consumes a predetermined time in said approach section, and for then maintaining said relay energized until the train occupies said detector section, a control circuit for clearing the approach signal adapted to be closed when the detector section is unoccupied provided said timing relay is energized or the extended locking section beyond the detector section in the established routeis unoccupied, a switch locking relay, means controlled by the home signal for controlling said locking relay to prevent an operation of the switch unless the home signal is in its stop position and the detector section is unoccupied, and means controlled by the approach signal for controlling said locking relay to prevent the establishment of a different route after the approach signal has been cleared unless said timing relay is energized or the extended locking section in said different route is unoccupied.

'7. In combination with a detector section of railway track including a'track switch, a home signal for governing tnaflic movements in the facing direction over the routes established by the operation of the track switch to normal and reverse, an automatic train stop adjacent the home signal for applying the brakes of a train passing said signal at stop, an approach section having an approach signal at its exit end for governing trafiic approaching the home signal, a timing relay for measuring the speed of an approaching train, means for energizing said timing relay only when a train consumes a predetermined time in said approach section, a control circuit for clearing the approach signal adapted to be closed when the established route is unoccupied for a given distance dependent upon the speed of an approaching train as measured by said timing relay within which the train may be stopped if its brakes are applied by said train stop, a switch locking relay, means controlled by the home signal for controlling said locking relay to prevent an operation of the switch unless the home signal is in its stop position and the detector section is unoccupied, and means controlled by the approach signal for controlling said locking relay to prevent an operation of the switch to establish a different route after the approach signal has been cleared unless said different route is unoccupied for said given distance.

8. In combination with a detector section of railway track including a track switch, a home signal for governing trafiic movements in the facing direction over the routes established by the operation of the track switch to normal or reverse, extended locking sections beyond the switch in said routes, an approach signal for governing traffic approaching the home signal, a signal control relay for clearing the approach signal, a switch control relay for openating the switch, normal and reverse correspondence relays arranged to be energized only when the switch and its control relay are in corresponding normal and reverse positions respectively, track relay-s for said extended locking sections, an energizing circuit for said signal control relay having two branches each including a front contact of the track relay for the extended locking section in a different route in series with a front contact of that correspondence relay which is energized when such route is established, and means for maintaining said circuit closed during the operation of the track switch comprising a third branch of said circuit which includes the front contacts of both of said track relays in series.

9, In combination with a detector section of railway track including a track switch operable to normal and reverse to establish diverging routes, extended locking sections in said routes beyond said detector section, an approach signal for governing traific movements over said routes, an approach section in each of said routes between the approach signal and said detector section, an approach locking stick relay arranged to be energized only when the approach signal is at stop, a circuit for clearing said signal adapted to be closed only when said approach and detector sections and the extended locking section in the established route are unoccupied, a switch locking relay which when deenergized prevents the operation of the switch, means for releasing said switch locking relay when the approach locking relay is released in response to the clearing of the approach signal for a movement over one of said routes but only if the extended locking section in the other route is occupied, means preventing the energization of said switch locking relay when said detector section is occupied, and means for preventing the reenergization of said approach locking relay when said signal is put to stop by a train enteringsaid approach section until the train enters said detector section.

10. In a system for electrically interlocking railway track switches, a home signal for governing trafiic movements over either of two routes selected by a first track switch one of said routes including a second track switch which in one of its two positions renders said one route unavailable, an approach signal governing trafiic appreaching said home signal, route circuits for said approach signal controlled by said switches and arranged to be closed to clear said signal when either of the two routes selected by the first switch is available and also during the operation of said first switch to a position to establish an available route, a manually controllable control relay for each switch operable only when said home signal is at stop, and means controlled by the second switch and rendered effective upon the clearing of said approach signal for preventing the operation of said first switch to the position required for said one route in response to the operation of its control relay until the second switch has been operated to the position required for such route.

11. In a system for electrically interlocking railway track switches, a home signal for governing traffic movements over either of two routes selected by a first track switch one of said routes including a second track switch which in one of its two positions renders said one route unavailable, an approach signal governing traffic approaching said home signal, route circuits for said approach signal controlled by said switches and arranged to be closed to clear said signal when either of the two routes selected by the first switch is available and also during the operation of said first switch to a position to establish an available route, a manually controllable control relay for each switch operable only when said home signal is at stop, and means effective if said control relays are operated to the positions required for said one route after the approach signal has been cleared for delaying the operation of said first switch until the second switch has assumed the position required for such route.

12. In a system for electrically interlocking railway track switches, a home signal for governing trafilc movements over either of two routes selected by a first track switch one of said routes including a second track switch which in one of its two positions renders said one route unavailable, an approach signal governing trafilc approaching said home signal, route circuits for said approach signal controlled by said switches and arranged to be closed to clear said signal when either of the two routes selected by the first switch is available and also during the operation of said first switch to a position to establish an available route, a manually controllable control relay for each switch operable only when said home signal is at stop, means governed by the control relay for the first switch when operated to the position required for said one route after said approach signal has been cleared for operating the control relay for the so send switch to cause the second switch to automatically assume the position required for such route, and means governed by the second switch for rendering the first switch responsive to said operation of its control relay only when the second switch has assumed said required position.

13. In a system for electrically interlocking railway track switches, a home signal for governing trafil: movements over either of two routes selected by a first track switch one of said routes including a second track switch which in one of its two positions renders said one route unavailable, an approach signal governing trafilc approaching said home signal, route circuits for said approach signal controlled by said switches and arranged to be closed to clear said signal when either of the two routes selected by the first switch is available and also during the operation of said first switch to a position to establish an available route, a manually controllable control relay for each switch operable only when said home signal is at stop, signal control means for controlling said route circuits to effect the clearing of said approach signal, and means controlled by the control relay for said first switch in the position required for said one route for operating the control relay for the second switch to the position required for such route in response to the operation of said signal control means.

14. In combination with a railway signal for relay for said trailing switch to the position required for said route.

15. In combination with a railway signal for governing traific movements over a route including a track switch facing said signal and a trailing track switch beyond said facing switch, manually controllable signal control means effective when operated to clear said signal provided both track switches are in the positions required for said route, a control relay for each switch for gov erning its operation, means governed by said signal control means for automatically operating the control relay for the trailing switch to cause that switch to assume the position required for said route in response to the operation of the control relay for the facing switch to the position required for said route, and means delaying the operation of the facing switch in response to said operation of its control relay until the trailing switch has assumed said required position.

RONALD A. MCCANN. 

